US2886865A - Apparatus for and method of making composite molds - Google Patents

Description

May 19, 1959 R. T. LEISK 2,886,865

APPARATUS FOR AND METHOD OF MAKING COMPOSITE MOLDS l Filed April 21, 1955 5 Sheets-Sheet 1 47M WMXWQ May 19, 1959 R. T. LElsK 2,886,865

APPARATUS FOR AND METHOD OF MAKING COMPOSITE MOLDs Filed April 21, 1955 s sheets-sheet 2 I M 8 LA t2 1NVENToR. ammf BY. M/W M0@ Mi/jv, w,

May 19 1959 R. T.`| E|SK 2,886,865

APPARATUS FOR AND METHOD OF MAKING COMPOSITE MOLDS Filed April 2l, 1955 3 Sl'xeeos--Sheerl 5 E IN V EN TOR.

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BY MMM ww XW @y APPARATUS FOR AND METHOD OF MAKING COIVIPOSIIE MOLDS Roland T. Leisk, Chicago, Ill., assignor to American teel Foundries, Chicago, 111.', a corporation of New ersey Application April 21, 1955, Serial No. 502,948

4 Claims. (Cl. 2236) This invention relates to composite molds and to a method for making them.

The invention particularly comprehends a method for forming a composite mold by blowing sand into a ilask, between the inner surface of the ilask and the outer surface of a pattern, to form a refractory wall between the surfaces.

As is Well understood by those familiar with the art of metal founding and casting, there are two broad classes of molds, the most common being known as allsand molds. The all-sand mold is formed by placing a flask over a pattern, filling the ask with sand, and packing the sand tightly around the pattern so that it assumes the contours of the pattern. After the pattern has been withdrawn, the cavity within the sand is filled with molten metal which solidies and assumes the shape defined by the pattern. The asks used in this type of arrangement are generally rectangular or regular in shape and open at the top and bottom. Of course, if the object to be cast has no at sides, it is necessary to employ a pair of flasks, the upper, known as the cope, receiving one part of the pattern, and the lower, known as the drag, receiving another part of the pattern. Sometimes it is necessary to employ a third or central flask, known as a cheek, which is positioned between the cope and the drag.

When the sand is emptied from the ask to remove the casting, the mold, as such, is destroyed, and the process must be repeated to cast another object.

ted States Patenti` O An advantage of the all-sand mold is that the refracl 4 tory character of the sand permits the ow of molten metal throughout the mold and results in a smooth casting having regular and even surfaces. Also the sand permits the normal contraction of the cooling metal without otering stresses that cause distortion and cracking of the casting.

The other class of molds is known as permanent molds. A permanent mold is usually formed of metal such as cast iron or of graphite, into which the molten metal is directly introduced.

This mold has obvious advantages over the all-sand mold, one advantage is that it can be reused, and another advantage is that it permits rapid heat dissipation which speeds up the entire molding operation by allowing the castings to be removed more rapidly after the metal solidifies.

However, the rigid character of the permanent mold interferes with the normal contraction of the cooling metal causing potential weaknesses, cracks and distortions n the casting. The use of a permanent mold is limited to casting operations involving castings of certain designs which permit free contraction from liquid to solid state.

Thus it has been discovered that neither the all-sand mold nor the permanent mold can be employed successfully in all types of casting operations.

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It is therefore, animportant object of this invention to provide a typeof mold suitable for all types of casting operations.

Another object of the invention is to provide a composite permanent type of mold having an outer heat dissipating holding form and an inner heat refractory facing form.

Another object of the invention is the provision of a casting apparatus that doesnt require the use of a conventional flask.

Another object of the invention is the provision of a permanent type of mold that will permit the normal contraction of cooling metal without offering resistances causing structural stresses or potential failures of the casting.

Yet another object of the invention is to provide a permanent type mold that will permit controlled heat dissipation from the cooling metal.

A more specific object of the invention is the provision ofa composite type mold having a metallic hold# ing or reinforcing form provided with an interior surface conforming to the general contours of the desired casting and a relatively thin layer of refractory material of generally uniform thickness backed and supported by the holding form.

To make anlall-sand mold, it is necessary to pack the sand in the ask around the pattern firmly so that the sand will retain its shape when the molten metal is introduced into the mold. Many methods have been devised to introduce and pack san-d into ilasks such as sandslinging machines, which employ centrifugal force of a rotating head, jolting machines, ramming machines, and manual packing and ramming. All of these methods are time consuming, however, and increase the cost of the molding operation.

It is therefore, another important object of this invention to provide a novel method of rapidly and uniformly introducing sand into an outer holding form.

A more specific object of the invention is to provide a method whereby sand can be blown into a holding form to form a refractory lining for the mold.

These and other objects of the invention will become apparent from an examination of the following description and drawings, wherein:

Figure 1 is a vertical sectional view of the cope portion of the holding form shown in sand blowing position,

Figure 2 is a view similar to Figure l but illustrating the drag portion of the holding form, and

Figure 3 is a vertical sectional View of a preferred embodiment of the invention including both cope and drag portions.

To describe the mold and the method of forming it, it will be seen from the drawings that the holding form or permanent portion of the mold designated generally at 10 comprises an upper or cope section l2 illustrated in Figure l, and a lower or drag section 14 illustrated in Figure 2.

Although the use of composite molds of the type embodied in this invention has been highly successful in the production of car wheels, it will be understood that their use is not limited exclusively to wheel molds and may prove to be of great value in other types of casting operations.

As may be seen in Figure l, the cope section 12 of the form is formed of a heat dissipating material such as cast iron and presents an inner surface 16 that denes a cavity 18 in the ask conforming generally to the contour of the article to be cast. The cope section may be provided with a plurality of vertical channels 19 having openings 20 at the upper surface 22 of the essence cope. These openings serve asv air vent holes. Another setV ofvertical channels 24 preferablyfspaced alternately of the air vent holes 2h having blow hole openings 26 at the upper surface 22 of the cope may be provided. Their function' is hereafter described. The ilaskA may be provided with a plurality ofl spaced riser channels preferably four (only one of which is shown) such as the one indicated at 28 which has an opening 30 at the upper surface 22. The cope may have, formed integrally with its lower edge, an outer peripheral flange 32 inset at 34 to form a circumferential groove 36.

In order to form the composite mold, the cavity 13 of the cope (as well as the cavity of the drag hereinafter described) is provided with a wall section or refractory lining of sand which abuts the surface 16 of the cavity.

To introduce the sand into the cavity of the cope, a sand blowing machine of any desired type may be employed. The arrangement utilized to blow the sand into the cope and drag is illustrated in Figures l and 2. The sand blowing machine A (which is not part of the invention itself) comprises `a magazine B having blow plate C across the opening at the bottom thereof. The blow plate C is provided with a plurality of blow holes D through which the sand is blown. Additionally, the machine has a platen E spaced from the blow plate and hydraulically actuated (not shown) for vertical movement toward and away from the blow plate.

The platen is provided with a central bore F receiving a centering pin G extending upwardly from the platen.

The half of the pattern 38 used in the cope of the mold presents an upper surface 40 which defines the contours of the object to be cast and presents a flat lower surface 42. The pattern may also be provided with an outer lower peripheral ange 44 inset at 46 to form a circumferential groove 48 alignable with groove 36 of the cope. The pattern 38 may be provided with a central bore 50 alignable with bore F of the platen by centering pin G.

Although the cope (and drag) section of the flask is rigid and therefore defines a cavity of definite size and shape, it is possible to use it to cast objects of varied central thicknesses within relatively limited margins by providing pattern 3S with removable center sections 52 according to the size of the center section of the desired casting.

Additionally, the pattern used may be provided with a plurality of vertical channels 53 containing vents 54 which permit the release of trapped air from the cavity 18 as hereinafter described.

To assemble the cope arrangement for the sand blowing operation, the lower surface 42 of the pattern is placed on the platen E of the machine with its central bore 50 aligned with bore F and with the pin G received in the bore 50.

A locating ring 56 may be positioned in groove 48 of the pattern and a hub core print H inserted in the recess 55 of section 52 of the pattern.

The cope is then placed over the pattern with the locating ring 56 being received in groove 36 of the cope as well as groove 48 of the pattern. The flanges 32 and 38 of the cope and pattern, respectively, may be clamped together by a conventional C-clamp (not shown).

It will be seen that under these conditions 1a relatively narrow cavity 118 of generally uniform thickness now exists between the upper surface 4@ of the pattern and the 4surface 16 of the cope.

A loose riser pattern section M is then placed in the center of each riser opening 2S of the cope and preferably secured to the pattern by a locating pin (not shown).

The hub core print H and the riser pattern sections M, although illustrated as in the drawings as being of wood, may be of any desired material.

A flat vent plate I is then placed over the upper surface 22 of the cope. The plate is provided with a plu- 4 rality of vertical apertures 58 and 60 which are mated with the cope openings` 20 and 26, respectively. Apertures 58 are each provided with a perforated vent 62 which permits the escape of air trapped in the cavity, but prevents the escape of sand. Spacer plugs 64 having vent holes 66 may be inserted in apertures S, and spacer plugs 68, each having a central bore 70 alignable with blow holes D, may be placed on the vent plate and tted in apertures 60.

The platen of the machine may then be elevated to raise the cope and the pattern until the upper surfaces of the spacer plugs are sealed against the lower surfaces of the blow plate, and the corresponding holes of the blow plate, vent plate, spacer plugs and cope are in alignment.

At this point, the cope is ready for the introduction of the sand into cavity 118 between cope surface 16 and pattern surface 40.

The sand J, a conventional bonding sand, may be blown from the magazine B into the cavity through the aligned blow openings of the blow plate, spacer plugs, vent plate, and cope to form a refractory facing wall between the holding form and pattern.

All of the vent openings in the cope and pattern permit the air trapped in the cavity, as well as the air blown in during the blowing process, to escape from the cavity and keep the sand in the cavity. All of the vertical channels in the cope become lled with the sand at this time.

The drag section 14 of the flask or permanent mold (illustrated in Figure 2) is generally similar to the cope section. The lower or exterior side 122 of the drag (the drag is shown inverted in Figure 2), however, is not flat but has an interrupted outer rim or extension 72 upon which the drag is supported when in an upright position. The center section 74 of the side 122 of the drag presents a dat surface 76 and is provided with a plurality of vertical channels 19 and 24 which correspond to the vent and blow openings, respectively, of the cope.

Inwardly adjacent rim 72, the side 122 is recessed at 78 and presents a horizontal surface 80 generally parallel to surface 76.

An intermediate section 82 between the rim and the center section is provided with a plurality of vertical channels 119 having vent stops 162 therein and with smaller gas vent openings 84 disposed in angular relationship to each other.

In order to plug the openings 84 of the drag, a stop plate K is inserted between the surface and a vent plate I'.

The vent plate I is then placed on surface 76 and also over the top of the stop plate. The vent plate may be provided with apertures 58 and 60 in its central section which are alignable with the vent and blow openings, respectively, of the drag.

Spacer plugs 64 and 68 may be placed over holes S8 and 60, respectively, on the upper surface of the vent plate, and spacer plugs 86 are placed on the upper surface of the vent plate outwardly of spacer plugs 68 and 64.

Thus it will be seen that the sand is introduced into the cavity of the drag in the same manner as it is into the cope.

In the preferred embodiment of the invention, it will be understood that the surface 40 of each half of pattern 38 is smooth and polished, while the inner surface 16 of the cope and/or drag is rough machined. This contrast of nishes insures that the sand wall sections will adhere to the cope and/or drag and permit the pattern to draw. After the pattern and pattern sections have been removed, the sand wall sections may be hardened, if desired, by a conventional mold wash and baking process.

When both the cope and drag sections are ready to assemble, they may be provided with preferably baked sand hub cores L.

To assemble them, the locating ring 56 is positioned in the grooves 36 of the respective flanges of the cope and ansehen drag sections and the anges are secured to each other by a conventional means such as a C-clamp (not shown).

rthus as illustrated in Figure 3, the composite mold comprises a permanent holding form or outer shell formed of a material such as cast iron that readily conducts heat and an inner shell or refractory facing layer of sand.

lt will be understood that because the making of this type of composite mold relies upon the sand blowing process described above, both the mold and the method of making it are inventions which necessarily are dependent upon each other.

l claim:

A method of making a composite mold comprising, introducing a pattern having a smooth surface into a metal reinforcing form having openings therethrough and having a rough inner surface generally conforming to the contours of the pattern spaced from the pattern, covering certain of said openings, blowing sand into said form through certain other of said openings to form a refractory wall of relatively uniform thickness between the surface of said form and the surface of said pattern, and uncovering said certain openings to permit the release of gas from said mold through said certain openings in a subsequent casting operation.

2. A method of making a composite mold comprising, inserting a pattern into a holding form having openings therein, covering certain of the openings, blowing sand into said form through certain other of said openings to form a wall of sand between said form and said pattern,

and mold part, removable spacer plugs between the vent plate and sand blowing machine defining passages therebetween, and removable spacer means between the vent plate and lower portion covering at least certain of the vent holes in the lower portion.

4. ln -an apparatus for forming a wall of refractory material between an inwardly facing surface of a permanent mold cope or drag section and an outwardly facing surface of a removable pattern disposed within a cavity of said mold section, said mold section having blow holes and vent holes extending therethrough and communicating with said cavity, the combination of: a refractory blowing machine having a at blow plate with blow holes extending therethrough; an independent vent plate disposed between the blow plate and the section and having blow and vent holes extending therethrough in alignment with the blow and vent holes, respectively, of the section, the blow holes of the vent plate also being in alignment with the blow holes of the blow plate; and separable removable spacer elements interposed between said plates and having pasageways in alignment with the sand blow and vent holes of the section, some of the passageways of said elements affording communication between the blow holes of the machine and the section, and other of said passageways aiording communication between the blow holes of the section and the atmosphere.

References Cited in the tile of this patent UNITED STATES PATENTS 525,040 Wood Aug. 28, 1894 2,663,059 Miller Dec. 22, 1953 2,720,687 Shaw Oct. 18, 1955 2,724,158 Davis et al. Nov. 22, 1955 2,785 ,447 Anderson Mar. 19, 1957 OTHER REFERENCES The Foundry, October 1950, page 162. Am. Foundryman, July 1953, vol. 24-1, pages 50 and 51.

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